A JEM 1200 EX TEMSCAN analytical electron microscope with a Tracor Northern X-ray microanalytical system and software is requested to replace the two routine transmission electron microscopes in the Department of Anatomical Sciences that are now over 12 years old. Although these instruments still function they cannot be interfaced with STEM, SEM or X-ray microanalysis accessory systems due to their early design and the necessity to have repair and accessory parts handmade (parts are no longer commercially available). At present there is no ion-pumped, LaB6 analytical transmission electron microscope with STEM/SEM and X-ray capabilities available to us at the University . The NIH supported research currently in progress in this Department involves the elemental analysis of endogenous electrolytes (P,S,Cl,K, Ca,Fe, Zn and Se) in isolated muscle filaments, honey bee and pigeon iron-containig cell, vertebrate eyes and annelid nerve cord, and histochemical and cell-surface marker verification by STEM/X-ray and electron diffraction analysis of frozen hydrated critical point dried and freeze dried specimens. Intracellular localization and quantification of the lower energy x-ray events (Na, Mg) and the more difficult to detect L lines of Ba and La necessitate and analytical system with optimum alignment and detection sensitivity, better than 15 nm resolution and advanced analytical software. High resolution STEM and SEM optics are required for visualization of low contrast cryosectioned tissue, immunocytochemical markers (colloidal gold) and surface ultrastructrue on Ca-ATP shortened and long isolated myosin filaments. All of the proposed projects are already in progress but are now severely limited by the lack of a central instrument that can offer the resolution, minimal contamination, data processing, high electron flux of an LaB6 gun and the flexibility to do more than one form of analysis on a tissue sample during EM observation. The acquisition of this instrument would markedly alter the quantity, accuracy and reproducibility of the microscopy related NIH funded research currently in progress in our Department. It would also permit the use of new "state of the art" analytical methods that are just not available now at this University or the neighboring academic and industrial centers.